📘 ❞ 07 – Memory and Programmable Logic :M. Morris Mano ❝ مذكّرة ــ إم موريس مانو

عن مذكّرة 07 – Memory and Programmable Logic :M. Morris Mano:
07 – Memory and Programmable Logic
BY :M. Morris Mano

Chapter 7
Memory and Programmable Logic
7.1 INTRODUCTION
A memory unit is a device to which binary information is transferred for storage and from
which information is retrieved whea & for processing. When data processing takes place,
information from memory is transferred to selected registers in the processing anit. Intermediate
and final results obtained in the processing unit are transferred back to be stored in memory,
Binary information received from an input device is stored in memory. and information
transferred to an output device is Wen from memory. A memory unit is a collection of cells
capable of storing a large quanlity of b i i in formation.
There are two types of de8tha t are used in digital systems: mndommcess memory
(RAM) and read-only memory (ROM). RAM stores new information for later use. The process
of storhg new infomation into memory is referred to as a menmy wrife eon. The process
of transferring the stored information out of memory is referred to as a memory read operation.
RAM can perform both write and read operations. ROM can perfom only the read operatim.
This means that suitable binary information is already stored inside memory and can
be retrieved or read at any time. However, that information cannot be altered by writing,
ROM is a pmgmmabk logic We(PL D). The binary information that is stored within such
a device is specified in some fashion and then embedded within the hardwam in a process is
refd to as pmgming the &vice. Tbe word "pro%ramming" hm refers to a hardware pm
cedure which specifies the bits that me inserted into the hardware cwfigumlio11 of the device.
ROM is one example of a PLD. Otber such units are the programmable logic array (PLA),
programmable array logic (PAL), and the field-programmable gate may (FPGA). A PLD is an
integrated circuit with internal logic gates connected through electronic path that khave similarly
to fuses. In the original state of the device, all the fuses ue intact+ Programming the
device invoIves blowing those fuses along the paths that must be removed in ordm to obtain